Nuclear Quadrupole Moment
nuclear quadrupole moment
[′nü·klē·ər ′kwäd·rə‚pōl ‚mō·mənt]Nuclear Quadrupole Moment
the quantity thatcharacterizes the deviation from spherical symmetry of the elec-trical charge distribution in an atomic nucleus. It has the dimen-sion of area and is usually expressed in sq cm. For sphericalsymmetry the nuclear quadrupole moment Q = 0. If a nucleusis extended along the axis of symmetry, then Q is a positivequantity, but if the nucleus is flattened along the axis, it isnegative. The value of the nuclear quadrupole moment variesover a wide range. For example, the nucleus of 
O, Q = -0.027 X 10-24 sq cm; for the nucleus of 
Am Q = +14.9 X 10-24 sq cm. Large moments are usually positive. Thismeans that when there is a substantial deviation from sphericalsymmetry, the nucleus has the shape of an elongated ellipsoid ofrotation.
V. P. PARFENOVA